MOSCOW — A U.S. congressional delegation is spending a week in Russia meeting with high-level government and security officials to investigate whether more could have been done to prevent the Boston Marathon bombings.

U.S. Rep. William Keating, D-Mass., whose district includes Cape Cod and the Islands, is one of six congressional representatives in the delegation.

Russia warned the U.S. in 2011 that bombings suspect Tamerlan Tsarnaev was a potential terrorist threat, but did not respond to U.S. requests for more information.

"We think there is some information that is vital for us to know that hasn't been made public yet," Rep. Dana Rohrabacher, the California Republican who is leading the delegation, said today after the congressmen laid a wreath at the site of a 2000 terrorist attack in Moscow.

The delegation includes Rep. Michele Bachmann, who announced early today she wouldn't run for re-election in 2014. She was scheduled to arrive in Moscow later today, a day after the rest of the delegation.

Tsarnaev, who was killed by police a few days after the April 15 attack, spent six months last year in Dagestan, a southern Russian province that is the center of a low-level Islamic insurgency. U.S. investigators are trying to determine whether Tsarnaev was radicalized during his time there.

Although the U.S. and Russian presidents have pledged to improve counterterrorism cooperation, both sides have accused the other of being less than forthcoming. U.S. officials have expressed frustration with the lack of information provided by Russia.

Russia's security services this month said it caught a U.S. Embassy employee in a clumsy attempt to recruit a Russian counterterrorism officer specializing in Dagestan. Russia accused the American of working for the CIA and expelled him.

In addition to Keating, Bachmann and Rohrabacher, who is chairman of the House Foreign Affairs Committee's Subcommittee on Europe, Eurasia and Emerging Threats, the congressional delegation includes: Steve King, Paul Cook and Steven Cohen.